compel: Print why memfd()-ing task fails

Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

compel/src/lib/infect.c

@@ -747,8 +747,11 @@ static int parasite_memfd_exchange(struct parasite_ctl *ctl, unsigned long size)
 	fd = (int)(long)sret;
 	if (fd == -ENOSYS)
 		return 1;
-	if (fd < 0)
+	if (fd < 0) {
+		errno = -fd;
+		pr_perror("Can't create memfd in victim");
 		return fd;
+	}
 
 	ctl->map_length = round_up(size, page_size());
 	lfd = ctl->ictx.open_proc(ctl->rpid, O_RDWR, "fd/%d", fd);